Antigenic preparation and isolation of such preparations

ABSTRACT

Purified Bordetella pertussis antigen having a molecular weight between 67,000 and 69,000 and determined by 12% (W/W) polyacrylamide gel electrophoresis and a proline glutamic acid ratio of substantially 1:1 as determined by amino acid analysis.

This is a continuation of application Ser. No. 08/058,227, filed May 10, 1993, now abandoned which is a continuation of Ser. No. 07/806,839 filed Dec. 9, 1991 (now U.S. Pat. No. 5,237,052) which is a continuation of Ser. No. 07/521,741 filed May 10, 1990, now abandoned which is a division of Ser. No. 07/142,261 filed Jan. 7, 1988, now abandoned which is a division of Ser. No. 06/894,435 filed Jul. 30, 1986, now abandoned which is a division of Ser. No. 06/729,257 filed May 1, 1985, now abandoned.

The present invention relates to antigenic preparations for use in acellular vaccines against Bordetella pertussis, and to a method for the isolation of such preparations.

Bordetella pertussis causes a serious and debilitating disease in humans, children being particularly susceptible, which is kept under control in the developed countries by large scale immunisation programmes. It has been found that immunisation is a very important factor in the reduction of the disease and that failure to vaccinate can lead to increased incidence of the disease. In practically all areas, immunisation is effected using a whole cell B. pertussis vaccine which has been found to be relatively effective in preventing the disease. However, it has been recognised that whole cell vaccines may suffer from several draw-backs. Thus, for example, in about 1 in every 10,000 children inoculated, clinical symptoms occur which may include fever, local reactions and persistent screaming. Further, it would appear that some batches of whole cell vaccine provide no protection at all while still being associated with the possibility of undesirable side-effects.

With the currently low occurrence of the disease in developed countries with immunisation programmes, the benefit/risk ratio is poorly defined, and many clinicians believe that the risks of inoculation outweigh the benefits gained by immunisation. As a result, many children are not inoculated and there is then a serious risk of a pandemic of whooping cough. Considerable research effort has, therefore, been directed towards the development of improved pertussis vaccines and especially acellular vaccines which lack the components associated with the toxic effects of the whole cell vaccines hitherto used whilst incorporating those components necessary to protect against the disease.

The search for a safer, effective, acellular B. pertussis vaccine has been hampered in the past by the paucity of information regarding the identity and mechanisms of action of the pathogenic, toxic and protective moieties of B. pertussis contained in the whole cell vaccines. Work has, therefore, been concentrated on isolating and purifying the 20 or more surface antigens of the B. pertussis organism and characterising their ability to induce immune reactions (see, for example, J. Am. Med. Soc., 248 (1) 22-23). Examples of antigens that have been suggested for investigation include lymphocytosis promoting factor (pertussis toxin/LPF) filamentous haemagglutinin (FHA), lipopolysaccharide (LPS), agglutinogens, dermonecrotic toxin (DNT), heat labile and heat stable toxins, polymorphonuclear leukocyte inhibitor factor, adenylate cyclase and other surface components (Pertussis Vaccine Workshop, Feb. 11, 1982, Bureau of Biologics, U.S.A.). Other proposed candidate antigens for investigation include tracheal cytotoxin and various outer membrane proteins.

An early extract vaccine was developed by L. Pillemer (Proc. Soc. Exp. Biol. Med. (1950) 75, 704-705) which was based on disrupted B. pertussis cells and found to provide protection but was not adopted commercially in view of the toxicity of the preparation.

Examples of more recent B. pertussis extract vaccines that have been suggested include those described in U.K. Patent Specification 2 083 358A (Takeda) involving removal of endotoxin from culture supernatants; French Patent Specification 2 047 886 (Institut Merrieux) involving extraction of a microbial suspension with an anionic surfactant; and Japanese Patent Specification 58-222032 (Teijin) which comprises a sub-unit protein based on pertussis toxin (LPF).

Much of the work carried out on acellular pertussis vaccines is concentrated on the possibility of basing such a vaccine on LPF. However, it is believed that most (if not all) of the adverse effects hitherto observed to be associated with pertussis vaccination are related to the toxin. In combination with tetanus or diphtheria toxoid and LPS, it is able to induce experimental encephalopathy in susceptible mice (L. Steinman, et al. Nature (1982) 299, 738-740; Redhead et al., Workshop on B. pertussis, Nat. Inst. of Biol. Standards & Controls, Holy Hill, Hampstead, London, 1983). Thus, LPF may, possibly, be responsible for brain damage should such complications occur after vaccination.

It has now been discovered that certain proteinaceous material, associated with adenylate cyclase activity, as hereinafter described, found in the cultures of B. pertussis, is capable of providing protection against challenge by B. pertussis when administered to experimental animals. This discovery that the proteinaceous material usually associated with adenylate cyclase activity is a major protective antigen against B. pertussis permits the preparation of vaccine formulations comprising antigenic preparations which are free from, or contain reduced amounts of, other known B. pertussis components which may be responsible for the toxic side-effects demonstrated by whole cell vaccines.

The term `proteinaceous material associated with adenylate cyclase activity (abbreviated to `ACAP` hereinafter) is used herein to refer to proteinaceous material which is extracted together with adenylate cyclase activity when extraction of the adenylate cyclase activity is performed using an aqueous, acidic (pH3) solution of glycine (0.25M)m. The ACAP as defined above may comprise the adenylate cyclase enzyme per se or a binding protein for the enzyme.

Adenylate cyclase activity was assayed by the method of Hewlett, E., and Wolff, J. (J. Bacteriol. (1976) 127, 890-898).

In a first feature of the present invention is provided a vaccine formulation for protection against B. pertussis which includes an antigenic preparation derived from B. pertussis comprising ACAP, optionally toxoided e.g. using formalin, glutaraldehyde or β-propiolactone, together with a pharmaceutically acceptable carrier therefor.

In more detail the ACAP may be detected by isoelectric focussing as two bands, one having an isoelectric point (pI) of, about 7.0, the other (diffuse) band having an isoelectric point of 7.2-7.4. Adenylate cyclase activity was associated almost entirely with the neutral band (pI≃7.0) but monoclonal antibodies to ACAP bound both bands strongly.

The ACAP in the above-mentioned preparations generally has a relative molecular weight of about 67,000 to 73,000, particularly 69,000, and an isoelectric point of 7.0-7.4 under preparative conditions as described infra.

By "relative molecular weight" is meant the apparent molecular weight as determined by 12% (w/w) polyacrylamide gel electrophoresis and standard molecular weight markers. The molecular weight of the antigenic proteins of the invention may thus be conveniently determined by the techniques described by U.K. Laemmli, Nature, 1970, 227, 680-685. Convenient standard molecular weight markers include, for example, bovine serum albumin, chymotrypsinogen A and ribonuclease.

Amino acid analysis has also shown that ACAP contains an unusually high proportion of proline, such that the proline: glutamic acid ratio is about 1:1 and this feature serves to distinguish ACAP from other B. pertussis proteins. A further distinguishing characteristic of ACAP is the fact that it cannot be detected by radio-iodination of its tyrosine residues by either the Chloramine T or the Iodogen methods.

According to a preferred embodiment of the present invention the above-mentioned ACAP is proteinaceous material which is characterised as having one or more of the following properties:

(i) a ratio of proline to glutamic acid of substantially 1:1;

(ii) the tyrosine residues are not iodinatable;

(iii) substantially free from intracellular, B. pertussis material;

(iv) a relative molecular weight of 67,000 to 73,000;

(v) an isoelectric point of 7.0 to 7.4, and

(vi) being acid-labile below a pH of about 3.

The above-mentioned antigenic preparations for use in the vaccine formulations according to the invention may, if desired, contain minor quantities of other antigenic compounds, in addition to the ACAP, for example, materials obtained together with the ACAP extracted from the B. pertussis organism. Such materials may comprise fragments of LPS and LPF which, in view of their possible detrimental side-effects, require toxoiding, e.g. with formalin. The antigenic preparations are, however, preferably substantially free from other antigenic components.

Adenylate cyclase has been previously isolated from B. pertussis (E. L. Hewlett et al., J. Bacteriol, 127, 890-898 and Proc. Nat. Acad. Sci., U.S.A., 73, 1926-1930) but there has been no suggestion that this material represents a protective antigen against B. pertussis. According to the work of Hewlett et al., only about 20% of the total adenylate cyclase activity from the B. pertussis organism, representing about 0.5% of the total enzyme, was found in the culture supernatant, the remaining 80% being bound to cells. An extraction process is therefore required by which the ACAP can be obtained in high purity and yield, in order to afford sufficient quantities, on a commercial scale, of ACAP for use in the above-mentioned antigenic preparations. A major difficulty to be overcome with such an extraction process is that the ACAP, among other proteins, is bound, part of it very firmly, to the LPS back-bone of the outer membrane. In the past, detergents have generally been used for the solubilisation of the membrane in order to liberate its associated proteins. However, the use of detergents for the extraction of outer membrane proteins from B. pertussis organisms has been found to have the following disadvantages:

a) the outer membrane is solubilised to form micellar aggregates comprising mixtures of outer membrane proteins;

b) the outer membrane proteins may be damaged;

c) new antigens, which do not exist in the bacterium, may be created, and

d) the extracted material is usually found to be water-insoluble after the detergent is removed.

We have now discovered that in contrast to the use of detergents, extraction of B.pertussis organisms using regulated, mildly acidic conditions results in the extraction of substantially increased yields (about 40×better than previously reported techniques) of adenylate cyclase from the outer membrane in a form which is water-soluble.

Thus, in an alternative aspect of the present invention is provided a method for the isolation of an antigenic preparation containing ACAP from B. pertussis which comprises treating a culture of B.pertussis cells with an aqueous amino acid buffer of pH 2.5-3.5, comprising a hypertonic concentration of said amino acid with respect to the cells, separating the cells from the resulting supernatant and isolating an antigenic preparation containing ACAP from the supernatant.

The buffer employed in the above-described method preferably provides a pH of about 3 and advantageously includes a mineral acid, preferably hydrochloric acid, as the acidic component of the buffer and either glycine or alanine as the amino acid. The treatment of the cells with the buffer is preferably effected at a temperature of 5° to 50° C., preferably 30° to 45° C., ideally 37° C., advantageously for 1 to 24 hours, preferably 10 to 20 hours with an amino acid concentration of 0.1-1M, preferably 0.25M. The ACAP is acid-labile and may be destroyed if the pH drops below 3 during extraction.

After incubation of the cells with the buffer, the cells are discarded and the supernatant obtained after centrifugation, e.g. at about 100,000 g (to remove all particulate matter), is, if desired, precipitated, e.g. using ammonium sulphate, cold ethanol or acetone.

The supernatant extract obtained has been tested in the Kendrick Test, as described below, and has been found to provide protection in mice against intracerebral challenge with B.pertussis. Control vaccines containing no adenylate cyclase activity were found to provide little or no protection against challenge with B.pertussis, suggesting that ACAP may, in fact, be the most important factor in immunity. Analysis of batches of non-protective whole-cell vaccine has also shown that non-protection tends to be associated with a lack of adenylate cyclase activity, further suggesting that ACAP may be the key antigen necessary for eliciting an immune response against B.pertussis.

The supernatant extract used in the Kendrick Test may, however, also contain the ACAP in small quantities complexed with other proteins including fragments of LPS, in which case, it may be desirable to purify further the material for use in the vaccine formulations according to the invention. Thus, for example, further purification may be effected by ion-exchange chromatography and/or by preparative isoelectro-focussing to eliminate complexed material. Alternatively, the two methods of purification may be combined, i.e. the material not retained by the DEAE gel (i.e. the non-complexed material) can be electrofocussed. The method of purification may also comprise chromatofocussing. After the above-described purification steps the ACAP may, if desired, be further purified, for example, by passing the material through an immunosorbent column containing an appropriate monoclonal antibody against the ACAP.

The antigenic preparations described above, including those prepared by the above-described method according to the invention, may be incorporated into a vaccine formulation for inducing immunity to whooping cough in man. For this purpose the antigenic protein may be presented in association with a pharmaceutically acceptable carrier or adjuvant.

Pharmaceutically acceptable carriers, in this instance, are liquid media suitable for use as vehicles to introduce the antigen into the patient. An example of such a carrier is saline solution. The antigenic protein may be in solution or suspended as a solid in the carrier.

The vaccine formulation may also comprise an adjuvant for stimulating the immune response and thereby enhancing the effect of the vaccine. Convenient adjuvants for use in the present invention include, for example, aluminium hydroxide and aluminium phosphate.

Conveniently the vaccine formulations are presented to contain a final concentration of antigenic protein in the range of from 0.01 to 5 mg/ml, preferably 0.03 to 2 mg/ml, most preferably 0.3 mg/ml. After formulation the vaccine may be incorporated into a sterile container which is then sealed and stored at a low temperature, for example 4° C., or may be freeze-dried.

In order to induce immunity in man to whooping cough one or more doses of the vaccine suitably formulated may be administered. It is recommended that each dose is 0.1 to 2 ml preferably 0.2 to 1 ml, most preferably 0.5 ml of vaccine. The present invention, in a further aspect provides a method for inducing immunity to whooping cough in man, comprising the administration of an effective amount of a vaccine formulation, as hereinbefore defined, to the host.

The present invention also includes the use of ACAP (as defined above) in the preparation of a vaccine for use in the induction of immunity to whooping cough in man.

The vaccines of the present invention may be administered by any conventional method for the administration of vaccines including oral and parenteral (eg. subcutaneous or intramuscular) injection. The treatment may consist of a single dose of vaccine or a plurality of doses over a period of time.

Vaccines according to the present invention may also comprise one or more other antigenic components such as, for example, suitably toxoided typhoid and diphtheria toxins, or other B.pertussis antigens, such as toxoided LPF, to reduce the likelihood of mutant strains of B.pertussis avoiding the concomitant immune response.

The following Examples serve to illustrate the invention:

EXAMPLE 1

Acid Glycine Hydrolysis and Preparation of Crude Outer Membrane Proteins.

The cells were harvested 3/4 of the way through exponential phase and spun down at 8000 g (Sorvall, GSA angle head) for 20 min at 4° C. The supernatant was siphoned off and the cells were immediately gently resuspended in distilled water to a density of 20-30 mg/ml dry weight of cells. One third of this volume of 1M glycine-HCl buffer, pH 3.0, was added under gentle stirring to obtain a final concentration of 250 mM glycine. The glycine solution contained EDTA (to obtain 5 mM in the final mixture) to stop enzymatic activity. The pH was checked and, where necessary, re-adjusted to pH 3.0 using 1-2M HCl. The mixture was gently stirred in a 37° C. water bath until the temperature equilibrated and then incubated overnight (18 hrs) at 37° C. (without stirring). The pH was then adjusted to 7.2-7.4 using 10M NaOH, which was added slowly to avoid local excess. The cells were sedimented at 5000 g for 20 min at 5° C., the supernatant was siphoned off, cooled in an ice-water bath to 1°-2° C. and 2 volumes of pre-cooled acetone (-20° to -40° C.) were slowly added to avoid the temperature rising above 1°-2° C. The mixture was then kept at -20° C. for 3-5 hrs and the precipitate collected in a pre-cooled (-10° C.) angle head at 4000 g for 20 min. The supernatant was siphoned off and discarded. The sedimented precipitate was dissolved in ice-cooled distilled water to approximately 1/20 of the original volume of cell suspension. The solution was then freed of insolubles and vesicles by spinning at 50000 g for 90-120 min at 5° C. The supernatant was collected and kept frozen or freeze-dried. 1% w/v mannitol was added before freeze-drying. Forty to eighty mg protein was obtained per gram dry weight of cells.

EXAMPLE 2

(a) Separation of the Crude Outer Membrane Protein Preparations by DEAE-Trisacryl Chromatography

A DEAE-Trisacryl column, 3×16 cm, was equilibrated with 0.025M TRIS, 0.035M NaCl buffer, pH 8.8, and the material obtained in Example 1 (up to 1 g of protein) dialysed against the equilibrating buffer and pumped at 60 ml/hour through the column. The fractions (99 drops per tube, ca. 5 ml) were combined in pools 1-13. Part of the total applied protein (approx. 1/4) is not retarded by the gel bed and would be collected as a large peak. The retained material was then eluted using 0.1, 0.2, 0.3 and 1.0M NaCl in 0.025M tris buffer (pH 8.8). The fractions were pooled and applied to a SDS-PAGE slab to establish the separation of proteins. The ACAP was present in the material unretarded by the column, as shown by SDS-PAGE, but was also present in the retarded material eluted by 0.2M NaCl.

(b) Preparative Flat Bed Isoelectrofocussing in Granulated Gel (IEF).

This was performed according to LKB recommendations (Application Note 198, LKB-Producter AB, Bromma, Sweden). A suspension of 4 g Ultrodex (LKB) and 5 ml of pre-blended Ampholine, pH 3.5-9.5 were suspended in distilled water to a final volume of 100 ml, poured onto a horizontal tray 10.8×24.3 cm and evaporated under a flow of air to the recommended limit. Layered strips of 3 paper wicks (LKB, 2117-106) soaked in 1:20 dilution of the same Ampholine in distilled water, were placed at each end of the tray. The material from Example 2a was embedded into the gel using an application template (2×9.4 cm) which was pressed into the gel at 1/3-1/4 of the distance along its length from the anodic end, the enclosed gel removed, transferred to a 10 ml disposable syringe, suspended in 3 ml of the said material from Example 2a (containing up to 500 mg protein) and finally injected back into the empty space formed by its removal. The gel was then smoothed with a spatula where necessary and left to equilibrate for 20 min. Meanwhile, one paper wick was soaked in a 1:100 dilution of phosphoric acid (sp.gr. 1.75) and added to the strips at the anodic end, and another in 1M NaOH and placed at the cathodic end. The tray support in the flat bed IEF apparatus (Pharmacia type FBE-3000) was cooled by running tap water (15° C.) during the run. The gel was run at a constant 8 watts.

The ACAP was detectable as two bands, one of pI 7.0, and the other (diffuse) band of pI 7.2-7.4. Adenylate cyclase activity was associated almost entirely with the central band (pI 7.0) but monoclonal antibodies to ACAP bound both bands strongly.

Using a metal template the gel bed was then divided into 30 parallel fields, the gel was scraped from each field using a spatula and transferred to test tubes containing 1 ml distilled water. The pH of each fraction was measured at this stage. The gel suspensions were then transferred into small plastic columns, eluted with 2 ml 0.2M ammonium bicarbonate buffer, pH 7.0, and the gel-free eluates frozen (-40° C.).

(c) Analytical Isoelectric Focussing

(i) The same procedure was used as for 2(b) above but a 12% polyacrylamide gel in the presence of 8M urea was used. The same results as for 2(b) were obtained.

(ii) The same technique, but using an agarose gel in the presence of 10% sorbitol, showed 4 immuno-reactive bands of pI 4.5 to 6.0. The band of pI 4.0 retained the majority of adenylate cyclase activity.

EXAMPLE 3

Purification of ACAP Using a Monoclonal Immunosorbent Column

Mouse ascitic liquid containing a monoclonal immunoglobulin specific for ACAP was precipitated at room temperature by the addition of 2 volumes of 27% w/v Na₂ SO₄ and left to stand for 2-4 hrs before being sedimented (2000 g for 15 min). The hybridoma which secretes the monoclonal immunoglobulin was deposited under the Budapest Treaty at the European Collection of Animal Cell Cultures, Porton Down, United Kingdom on 5th Jan. 1990 under accession number 90010501. The sediment was redissolved and dialysed against PBS. Five hundred mg of this protein (UV determination) was coupled to 70 ml of packed CNBr-Sepharose CL4B following the manufacturer's instructions (Pharmacia). Sephadex G-50 (medium) was applied to a 500 mm×25 mm column to a bed height of 220 mm. After washing the column with elution buffer (0.2M ammonium bicarbonate, pH 7.0, containing 0.01% Thiomersal) a 5 mm thick layer of No. 12 Ballotini glass beads was poured on top of the Sephadex bed. After further washing, the immunosorbent gel was poured onto the Ballotini glass bead layer, this being separated from the

Sephadex bed allowing for separation of both. The column was further washed with elution buffer, and finally another Ballotini glass bead layer was placed on top of the 100 mm high immunosorbent bed to protect the top of the column.

To separate the ACAP on the immunosorbent column, 180 ml of the unretained eluate from the DEAE-Trisacryl Separation (Example 2) containing 1 mg/ml protein (Lowry), was applied at 5° C. to the immunosorbent column at 0.25 ml/min, washed with elution buffer (0.2M ammonium bicarbonate, pH 7, 0.01% w/v Thiomersal) and, after the base-line had stabilized, 50 ml 6M Urea in elution buffer was applied to the column to elute the adsorbed material. The positioning of the immunosorbent material over a Sephadex G-50 bed allowed for the simultaneous separation of the protein from urea during the run.

EXAMPLE 4

Culture of B.pertussis

The defined medium used for growth of the organism was based on the formula of Steiner and Scholte (1971) as previously described (Novotny and Brookes, 1975). All cultures were grown at 36°-37° C. The liquid cultures, in loosely capped shake flasks (500 ml conical flask with 200 ml medium), were inoculated with a culture grown for 48 hrs on Cohen-Wheeler medium with 2% agar and 5% horse blood and agitated to give a gas exchange rate of 20-40 μM O₂ /hr. Such liquid cultures were used to inoculate the medium in 5 liters or 70 liters all-glass fermentors, while the pH was maintained at 7.6 by the controlled addition of 2M HCL and the dissolved oxygen saturation at 5-10% by impeller agitation. The cultures were harvested before the end of the exponential phase, i.e. after approximately 36 hrs incubation (Novotny and Cownley, 1978).

EXAMPLE 5

Kendrick Test

This was performed according to W.H.O. Requirements for Pertussis Vaccine using MF1 or NIH Mice (OLAC, category 3, free of most pathogens including B.bronchiseptica), weighing 14-16 g. The antigen, in 0.5 ml volumes, was inoculated intraperitoneally and comprised a top dilution and three four-fold serial dilutions. After two weeks the mice were challenged intracerebrally using the recommended challenge strain 18-323 (100-200 LD₅₀). The number of survivors in each group was used for calculation of the ED₅₀ and of the relative potency in respect to the British Pertussis Reference Vaccine 66/84 using a program of parallel line probit analysis. A comparative test was also preformed using an FHA/LPF vaccine. The results are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                         PROTECTIVE POTENCY OF BORDETELLA PERTUSSIS                                     FRACTIONS IN THE MOUSE PROTECTION TEST                                         AGAINST B.PERTUSSIS 18-323                                                     INTRACEREBRAL CHALLENGE ("KENDRICK TEST")                                                             Relative  41.U. in μg                                                       potency   protein (=                                                   ED.sub.50                                                                              I.U./μg                                                                               single                                        Material       μg   protein   human dose)                                   ______________________________________                                         Crude glycine hydrol. of                                                                      20      0.02       190                                          B.pertussis hydrolysed                                                         at 37° C.                                                               Crude glycine hydrol. of                                                       B.pertussis,                                                                   hydrolysed at 4° C.                                                                    77      0.003     1333                                          Hydralysed at 37° C.                                                                   20      0.011      363                                          Hydrolysed at 53° C.                                                                   149     0.001     4000                                          B.pertussis immunopurified                                                                    19      0.011      364                                          adenylate cyclase                                                              FHA/LPF vaccine                                                                               77      0.003     1333                                          ______________________________________                                    

EXAMPLE 6

Amino Acid Analysis of ACAP

The amino acid analysis was carried out using a Rank Hilger Chromaspek amino acid analyser. Samples were prepared by the addition of 250 μl of 6N HCl (diluted from BDH Aristar grade) containing 0.1% (w/v) phenol to the dried sample material in a thick-walled Pyrex test-tube (7.5×1.2 cm) Tubes were then drawn out in an oxygen-natural gas blow-torch flame in order to produce a narrow orifice. After freezing the contents in a solid CO₂ -ethanol bath, each tube was connected via a manifold and trap to a high vacuum pump and left for ten minutes to remove air. The tubes were then sealed off and placed in an oven at 110° C. for hydrolysis. The hydrolysed samples were dried in a vacuum desiccator over sodium hydroxide pellets. The dried residue was dissolved in 250 μl of amino acid analyser starting buffer for automated analysis.

The amino acid values shown in Table 2 are averages of the results obtained from duplicate 24, 48 and 68 hour hydrolyses except in the case of valine and isoleucine where the 68 hour hydrolysis values were used.

Values for cystine, cysteine and tryptophan could not be determined by this method.

                  TABLE 2                                                          ______________________________________                                                           residues                                                     ______________________________________                                         Aspartic acid (+Asparagine)                                                                        48                                                         Threonine           33                                                         Serine              33                                                         Glutamic acid (+Glutamine)                                                                         62                                                         Proline             60                                                         Glycine             77                                                         Alanine             82                                                         Valine              54                                                         Methionine           4                                                         Isoleucine          22                                                         Leucine             50                                                         Tyrosine             7                                                         Phenylalanine       11                                                         Histidine           13                                                         Lysine              19                                                         Arginine            37                                                         ______________________________________                                    

EXAMPLE 7

Vaccine Formulations

Vaccines for use in immunisation may be prepared by conventional techniques with the following constituents:

a) Diphtheria, Tetanus and Pertussis Vaccine in Simple Solution

Each 1 ml of vaccine contains:

    ______________________________________                                         Diphtheria Toxoid       >60 I.U.                                               Tetanus Toxoid          >120 I.U.                                              Pertussis Antigen according to the                                                                     >0.363 mg                                              invention                                                                      Sodium borate           <10.03 mg                                              Succinic acid           <3.10 mg                                               Thiomersal              0.04-0.2 mg                                            Sodium chloride         <8.5 mg                                                Water                   to 1 ml                                                ______________________________________                                    

b) Adsorbed Diphtheria, Tetanus and Pertussis Vaccine

The diphtheria, tetanus and pertussis components are adsorbed onto aluminium hydroxide gel by standard techniques.

Each 1 ml of vaccine contains:

    ______________________________________                                         Diptheria Toxoid     >60 I.U.                                                  Tetanus Toxoid       >120 U.L.                                                 Antigen according to the invention                                                                  >0.363 mg                                                 Insoluble aluminium salts                                                                           <Equivalent to 0.093                                                           mmols (2.5 mg)Al.                                         Sodium borate        <8.01 mg                                                  Succinic acid        <2.48 mg                                                  Thiomersal           0.04-0.2 mg                                               Sodium chloride      <6.8 mg                                                   Water                to 1 ml                                                   ______________________________________                                    

c) Pertussis Vaccine

Each 1 ml of vaccine contains:

    ______________________________________                                         Antigen according to the invention                                                                     >0.363 mg                                              Thiomersal              0.04-0.2 mg                                            Sodium chloride         <8.5 mg                                                Water                   to 1 ml                                                ______________________________________                                     

I claim:
 1. A purified Bordetella pertussis antigen characterized by the following features:a relative molecular weight of between 67,000 and 69,000 as determined by 12% (W/W) polyacrylamide gel electrophoresis; and a ratio of proline to glutamic acid of substantially 1:1 as determined by amino acid analysis. 